The present invention relates to an improved sound absorbing material and more specifically, to a sound absorbing material comprising a blended matrix of man-made fibers, a co-binder, and fibrous cellulose or cellulose based material.
Automobile manufacturers typically use sound absorbing materials to line various compartments of an automobile, such as the engine compartment, to inhibit noise from entering a cabin or interior portion of a vehicle. The sound absorbing material may also line the interior of the vehicle, such as the headliner and floorboard, to absorb sound created from within the cabin. Automobile manufacturers require the material to meet specific standards. For instance, the sound absorbing material must withstand certain temperatures without burning or melting. To test this standard the sound absorbing material is subjected to a flame test. In the open flame test a sound absorbing material is introduced to an open flame for a specific period of time at a specific distance from the material sample. It is preferable that the sound absorbing material should not melt or burn, or if the material burns it should have a self-extinguishing characteristic.
Pure polyester is known in the art for use as a sound absorbing material and generally has good sound absorbing characteristics. However, it has been found that pure polyester does not perform well in the open flame test because the material burns and melts at high temperatures. Additionally the pure polyester generally softens and sags at temperatures above 450 degrees Fahrenheit. In an attempt to improve performance of the sound absorbing material in the flame test as well as increase the sound absorbing characteristics, some portion of fiberglass was added to the polyester sound absorbing material. Although fiberglass performed better in the flame test and had good sound absorption characteristics, it has a major drawback. Fiberglass may cause irritation to human skin, eyes and respiratory systems. Generally, the smaller the fiber sizes the harsher the irritation. Thus, although fiberglass is good in one respect it is not quite as appealing in others.
In view of the deficiencies in known materials, it is apparent that a sound absorbing material is needed having good sound absorbing qualities, having a decreased amount of fiberglass, which passes moisture absorption testing, and will pass the flame tests of automotive manufacturers.